Matt Clement lasted three innings, Sammy Sosa struck out four times and the Cubs failed to capitalize on a prime opportunity to pick up a game on division-leading Houston, remaining 1½ games behind the Astros with seven games left.

They also fell to 2½ games behind wild-card-leading Florida. Clement (13-12) was pulled with no outs in the fourth, allowing six runs on six hits and two walks. It was his shortest stint since Aug. 19 and followed on the heels of poor outings from Carlos Zambrano and Juan Cruz in Friday's doubleheader.

Mark Prior, who's 8-1 since the All-Star break, will try to stop the bleeding Sunday when he faces left-hander Oliver Perez in the series finale.

The Cubs led 1-0 with two outs in the third when Tike Redman dropped a double in front of a diving Moises Alou in left. Jack Wilson then singled to tie the game. Clement dug his own grave in the fourth, walking the first two batters and hitting Carlos Rivera to load the bases. Abraham Nunez hit a chopper to third and beat it out for an infield hit, giving the Pirates a 2-1 lead. Ex-Cub Jose Hernandez grounded a single between third and short to bring home two more runs, and pitcher Ryan Vogelsong (2-1) singled to right after squaring to bunt on a 1-2 pitch, loading the bases again.

"They just hit it where we weren't and beat us that way," catcher Paul Bako said. "The key to that inning was a couple walks and a hit batter. It's hard to put out a fire when an inning starts that way."

Baker pulled Clement for Mark Guthrie, but Redman's hit toward left glanced off the glove of shortstop Alex Gonzalez, bringing in two runs to make it 6-1.

The play that epitomized the Cubs' plight occurred in the sixth with Simon on first and two outs. Bako struck out on a wild pitch that got away from catcher Jason Kendall, whose throw to first sailed into right field. Simon chugged around the bases and was thrown out trying to slide around Kendall, who caught a high, arching throw from right fielder Matt Stairs.

"I wouldn't do anything different," Simon said. "I tried to sneak in on the back side and he recognized that."

Sosa is 2-for-13 in the series and hitting only .203 in September. He and Alou are a combined 3-for-22 in the series and have only 21 RBIs since Sept. 1. Baker will move Sosa into the cleanup spot Sunday to shake things up.

"When he gets in one of these ruts, it seems like it stays for a while and then he gets hot again," Baker said.